1. Technical Field
The present invention relates to an image forming apparatus and an image forming method that form an image by developing a latent image formed upon a photosensitive member using a liquid developer composed of toner and a carrier, transferring the resulting developer image onto a transfer material such as recording paper, and furthermore fixing the toner image onto the transfer material onto which the toner image was transferred.
2. Related Art
Various image forming apparatuses that develop and visualize latent images using a high-viscosity liquid developer in which is dispersed toner composed of solid components within a liquid carrier have been proposed. The developer used in such image forming apparatuses has solid content (toner particles) suspended within an electrically-insulative, high-viscosity organic carrier (carrier liquid) composed of silicone oil, mineral oil, cooking oil, or the like; the toner particles are extremely small, with a particle diameter in the vicinity of 1 μm. By using such small toner particles, a wet-type image forming apparatus is capable of realizing higher image qualities than dry-type image forming apparatuses, which use powder toner particles having a particle diameter of approximately 7 μm.
With past electrophotographic-type image forming apparatuses that consume a liquid developer, image formation has been carried out by first transferring a toner image formed by a developing unit into a transfer member, and then performing a secondary transfer of the transferred toner image onto a transfer material such as recording paper. With respect to the transfer member onto which the toner image is transferred by the developing unit, a belt-type member, a roller-type member, or the like is used, and the surface of the transfer member can be repeatedly used any number of times. Accordingly, the surface of the transfer member following the secondary transfer is prepared for a new image formation after remaining toner that still adheres to the transfer member is removed by a cleaning unit provided so as to make contact with the transfer member.
JP-A-2008-209426 discloses a cleaning apparatus used in an image forming apparatus that employs liquid developer, the cleaning apparatus including a preliminary cleaning unit that causes toner particles that have adhered to the surface of an image bearing member to be suspended in a carrier liquid, a toner particle collecting unit that collects suspended toner particles using static electricity, and a carrier liquid collecting unit that collects the carrier liquid from the surface of the image bearing member. According to this cleaning apparatus, the toner particle collection efficiency can be improved by the preliminary cleaning unit causing the toner particles to be suspended in the carrier liquid and then collecting the toner particles by causing the toner particles to undergo electrophoresis through the static electricity applied by the toner particle collecting unit.
In addition, JP-A-2008-209426 also discloses suppressing the use of carrier liquid by reusing the carrier liquid used by the preliminary cleaning unit. FIG. 6 of JP-A-2008-209426 illustrates a cleaning liquid supply/reuse apparatus 400 that reuses carrier liquid collected by an intermediate transfer member cleaning apparatus 30.
The cleaning liquid supply/reuse apparatus 400 includes four tanks, or a cleaning liquid tank 401 that stores the cleaning liquid, a toner particle collection tank 305 that holds toner collected by a toner particle collection roller 32, a waste liquid tank 402 that stores carrier liquid and cleaning liquid collected by a blade 33, and a mixing tank 404 that pumps the liquids in the cleaning liquid tank 401 and the waste liquid tank 402 using a pump 403 and mixes those liquids.
The mixture of the carrier liquid and cleaning liquid in the mixing tank 404 is supplied to a preliminary cleaning roller 31 by the pump 403. Meanwhile, the mixture of the carrier liquid and the cleaning liquid collected by the blade 33 is sent to the mixing tank 404 after being filtered in the waste liquid tank 402. Furthermore, the toner collected by the toner particle collection roller 32 is wiped off by a toner particle collection blade 35 that makes contact with the surface of the toner particle collection roller 32, and is then held in the toner particle collection tank 305.
However, with the cleaning liquid supply/reuse apparatus 400 disclosed in JP-A-2008-209426, four tanks, or the cleaning liquid tank 401, the toner particle collection tank 305, the waste liquid tank 402, and the mixing tank 404, as well as the components, pumps, and so on to connect each of the tanks, are necessary in order to reuse the cleaning liquid, which makes it difficult to achieve a reduction in size of the cleaning apparatus and, by extension, in size of the image forming apparatus as well.
In addition, with the cleaning apparatus in JP-A-2008-209426, it is necessary to dispose the preliminary cleaning unit, the toner particle collecting unit, and the carrier liquid collecting unit so as to make contact with the surface of the intermediate transfer member, which is the entity to be cleaned. In such a case, a certain amount of surface area on the intermediate transfer member is required, but in the case where the surface area of the portion that can be cleaned is limited, as with a belt-type intermediate transfer member, installing the cleaning apparatus is difficult to begin with. Furthermore, increasing the number of components makes it difficult to achieve a reduction in size of the cleaning apparatus and, by extension, in size of the image forming apparatus as well.